The present invention is directed to the interconnection of different communication networks and more particularly to a device and method for routing information signals between the networks.
A communication network is the interconnection of communicating devices (e.g., telephones, computers, modems, video transceivers) by way of communication channels so that information signals are conveyed between the communicating devices. The communication channels can be different types of media through which the information signals are conveyed. Communication channels can be implemented for example as metallic wires, coaxial cables, fiber optic cables, and open air (for wireless systems). The communicating devices are any device which can transmit and/or receive information signals.
During the past several years, there has been a tremendous increase in the use of communication networks known as data networks. One particular well known and popular data network is commonly referred to as the Internet. A data network is a communication network in which information signals are conveyed throughout the network in digital form. That is, digital bits representing some type of information (e.g., digital data, digitized voice, digitized video, facsimile data) are grouped together along with other bits of data, known as header bits or trailer bits, which represent information about data being transmitted and/or the particular communication protocol being employed by the network. Each group of bits is commonly referred to as a packet. Each packet is typically part of or associated with an information signal. The information signal can be data, voice, or video communication signals.
The protocol represents a particular set of rules by which all or some of the communicating devices within a data network (and other types of communication networks) initiate communication, convey information and terminate communication. Thus, all or some of the communicating devices (e.g., computers, modems, facsimile machines and other digital communication devices) which are part of a data network should transmit and receive information in accordance with a protocol. Typically, protocols are established communication standards that are well defined and followed by data networks. For example, the established protocols for the Internet are the well known IP protocol suite and associated upper level protocols (e.g., TCP/IP, UDP) which are followed by all users of the Internet.
The packets are routed throughout the network via a well known scheme commonly referred to as packet switching. In a packet switching data network, each packet is routed from point to point within the data network. The path taken by one packet representing part of an information signal can be different from the path taken by other packets of that same information signal. In essence, a network routing scheme or algorithm dictates the path to be taken by a packet at each point of the network until that packet arrives at its destination point. Some of the header bits or trailer bits contained within a packet are typically used to encode information about the origin, destination, and the order of the packet in relation to other packets. Also, the routing algorithm used by communicating devices throughout the network allows packets associated with a particular information signal to arrive at their proper destination. Packet switching networks are generally viewed as efficient networks for many types of communications when compared to other communication networks that do not use packet switching. One of the main reasons for this general view is due to the ability of packet switching networks to better able to recover from faults such as system equipment failure and communication link failures.
Prior to the advent of packet switching networks, many communication networks used a different scheme known as circuit switching. In contrast to packet switching, circuit switching allocates network resources to define a specific communication path or channel through which information is to be conveyed between two points within that network. Circuit switching is widely employed in the design of telephony systems such as the well known POTS (Plain Old Telephone System) networks or the PSTN (Public Switched Telephone Network) in which a particular communication path, or channel or circuit is allocated specifically for particular users who wish to communicate with each other. For example, in the case of a PSTN communication network, party A wishes to call party B via a telephone interfaced to the PSTN communication network. Party A dials party B""s number. The dialed number, which is part of the signaling used by the PSTN protocol to initiate communication between a calling party and a called party, is recognized by the network and causes the network to establish a communication path between party A and party B. This particular communication path is used by Party A and Party B until the call is terminated by one of the parties. The information signals (a continuous stream of digitized voice samples) are conveyed over the same communication path until one of the parties terminates the telephone conversation. Circuit switched networks, such as the PSTN, are generally viewed as inefficient relative to packet switching networks particularly for sporadic or bursty communications because of the manner in which circuit switching networks allocate their resources.
Circuit switched communication networks are typically associated with telephony networks. Current telephony networks are typically digital versions of earlier telephony systems that used electro-mechanical switching to route analog voice signals between users of such systems. Thus, infrastructures of circuit switched communication systems (mostly telephony systems) throughout the world were firmly established even before the advent of digital communications. With the coming of digital communications, many of these networks now transmit their information signals in digital form but still continue to use circuit switching.
Packet switching networks and circuit switching networks are incompatible in that they use different protocols. Users of packet switched communication networks cannot communicate with users of circuit switched networks. Wholesale conversion of circuit switched communication networks to packet switched communication networks is very unlikely because of the costs involved. There wilt, therefore, be an extended period of time during which both types of networks will coexist. In many circumstances, there may be a need for users of circuit switched networks to communicate with users of packet switched networks. There is also a need for users of incompatible packet switched networks to communicate with each other because not all packet switched networks use the same protocol. More importantly, it is desirable for users of circuit switched communication networks to use the resources of a packet switched network. That is, the circuit switched user would actually transmit and receive information signals via a packet switched network. This is desirable because in many such instances a circuit switched user would actually be using a more efficient and less costly network to communicate with another circuit switched user. A particular type of communication system known as Packet Telephony applies this very philosophy. Packet Telephony is the integration of speech compression and data networking technologies to provide traditional and enhanced telephony services (e.g., voice calls, FAX, voice mail,) over packet switched networks rather than the Public Switched Telephone Network (PSTN). For example, if two users of the PSTN (Person A and Person B) are having a telephone conversation, the analog speech signals from A""s microphone are digitized by an A/D converter, typically at 8000 samples/second, 8 bits/sample, totaling 64 Kbits/sec. These digital speech samples are then compressed to reduce the number of bits needed to represent them. The compression ratio is typically in the range of 8:1 to 10:1 yielding a bit rate in the range of 6400 bits/sec to 8000 bits/sec. The compressor""s output is then formed into packets, protocol header bits and trailer bits are added and the packets are transmitted through a packet switched network to the packet telephony system serving Person B. When the packets are received by Person B""s system, the protocol header bits and trailer bits are removed and the compressed speech data is sent to a decompressor. The decompressor output is connected to a D/A converter which drives Person B""s speaker. For a typical 2-party call, the packet telephony systems at each end simultaneously implement both the transmit and receive functions. The A/D (analog to digital converter), D/A (digital to analog converter), compressor, decompressor are well known electronic circuits used by those of ordinary skill in the art of electronics or electrical engineering. Thus, packet telephony is an example of a circuit switched network (e.g., the PSTN) interacting with a packet switching network.
The interaction of packet and circuit switched networks or the interaction between incompatible packet switched networks requires devices called gateways that provide cross conversions of voice, data, video signals and protocol information between the two types of communication networks. The gateway is able to understand the protocol used by the different communication networks and thus acts as a translator for the networks. Gateways enable communication to be established between otherwise incompatible networks. For example, gateways allow phones or other devices on the PSTN (a circuit switched network) to communicate with telephony devices connected to data networks. For Packet Telephony systems, gateways allow, for example, long distance telephone calls originating and terminating on the PSTN to be carried over packet switched data networks at a reduced cost. In essence, a gateway is a communications device which interconnects two or more incompatible communication networks and enables users of any of the networks to communicate with other network or use the resources of other networks. Service providers, which are entities such as local telephone companies, and commercial long distance carriers typically own the gateways and control a user""s access to communication networks via these gateways.
Because of the manner in which packets of information are routed in packet switched networks, the quality of service (QoS) of any established communication that uses the resources of a packet switched network will vary. The term xe2x80x98established communicationxe2x80x99 as used herein is defined as the process of at least two users (of the same or different networks) initiating communication with each other in accordance with their respective protocols and the users conveying information to each other over a communication network. The quality of service (QoS) of the xe2x80x98established communicationxe2x80x99 is a performance level criterion that sets the conditions under which an xe2x80x98established communicationxe2x80x99 is deemed unacceptable due to deteriorating conditions of the communication network through which information signals are being conveyed.
Specifically, the quality of service is a function of well known network characteristics such as bit error rate, packet error rate, packet loss rate, data jitter or delay variation and other factors that deteriorate the quality of established communication between users. Many times the quality of the established communication deteriorates to an unacceptable level resulting in loss of data or unintelligible voice signals in the case of packet telephony systems. However, the deterioration may be temporary as the quality of the established communication may once again become acceptable. The QoS parameters and acceptable values can be defined by either the users or the service provider or any other entity associated with the use, maintenance, or design of the communication equipment.
The variation in the quality of the xe2x80x98established communicationxe2x80x99 for the packet switched networks (particularly for public data networks such as the Internet) is unpredictable and many of these networks offer no quality of service guarantees. It would, therefore, be desirable for users to have access to various networks and use those networks in a judicious manner such that when a network""s quality of service deteriorates to an unacceptable level, an xe2x80x98established communicationxe2x80x99 can be rerouted to a network that has an acceptable quality of service. It is further desirable that the rerouting be done without any disruption to the xe2x80x98established communicationxe2x80x99 as any disruption will result in additional loss of data. A disruption is defined as any interruption of transmission and or reception of information signals resulting in loss of data or unintelligible voice, video or other signals.
Thus, there exists the need to have a system and method for interconnecting incompatible communication networks to each other such that the quality of service of the interconnected networks, including the network through which an established communication is conveyed, can be monitored. Also, there exists the need to measure the quality of service for each of the interconnected networks and develop a criteria for categorizing the measured quality of service as being acceptable or unacceptable.
The present invention provides a communication controller for routing information signals between a plurality of communication networks. The communication controller has the ability to monitor and measure the quality of service of the networks and also contains criteria that define acceptable quality of service for the networks. When the quality of service of a communication network through which the information signals are being routed has deteriorated to an unacceptable level, the communication controller reroutes the information signals through another of the plurality of communication networks whose quality of service is acceptable.
The communication controller comprises a Network Port configured to receive control signals based on quality of service network characteristic measurement data and network criteria data received by the communication controller, the Network Port is further configured to receive information signals from the plurality of networks and route the information signals in accordance with the control signals.